1. Field of the Invention
The present invention relates to a method for production of pure uranium trifluoride characterized by heating a mixture of uranium tetrafluoride and uranium nitride in an inert gas stream or under vacuum.
2. Description of Prior Art
As means of producing uranium trifluoride, two methods have been so far adopted. The present inventor comments below on these two prior art methods.
One is characterized by heating a UF.sub.4 to a high temperature in an atmosphere of hydrogen gas free from oxygen and moisture to reduce the UF.sub.4 to UF.sub.3. And the other is characterized by heating a uranium metal in a stream of hydrogen gas to convert the uranium metal to uranium hydride, decomposing the uranium hydride to finely divide uranium metal powder under additional elevation of temperature and then fusing the mixture of UF.sub.4 and the finely divided uranium metal powder to form UF.sub.3 in a stream of argon gas at high ignition temperatures. Each of these two methods has its own demerit as noted below.
In the former case, because the hydrogen fluoride formed along with UF.sub.3 is highly corrosive, it is very difficult to find materials for a reactor which are resistant to the corrosive effect of the hydrogen fluoride at high temperatures.
In the latter case, the finely divided uranium metal powder is very hard to handle and is apt to be contaminated with impurities, e.g. oxygen. In addition, the uranium metal powder itself is easily sintered, and therefore the reaction is rarely completed satisfactorily.
Those skilled in the art have so far believed that uranium tetrafluoride does not react with uranium nitride.
However, I, the inventor of this invention have found that uranium trifluoride can be easily produced by heating a mixture of uranium tetrafluoride and uranium nitride in a stream of inert gas (rare gas) or under vacuum.